Breed × Nutritional Environment Interactions for Beef Female Weight and Fatness, Milk Production and Calf Growth

Abstract

Female weight, fatness, milk production and calf growth were measured to determine seasonal patterns for 120 Angus, Hereford, Angus × Hereford and Hereford × Angus 2-yr-old females grazing fescue or 60% fescue-40% legume. Females calved January through March and calves were weaned in October in each of the 3 yr of the experiment. Preliminary analyses indicated that Angus × Hereford and Hereford × Angus females responded in a similar manner for all variables measured. Angus-Hereford females responded to increased nutrient supply provided by fescue-legume pasture (as compared with fescue) by increasing (P<.05) fatness, especially during late spring, and, to a lesser degree, by increasing (P<.05) milk production and calf growth. Hereford and Angus females, however, responded by increasing (P<.05) milk production (especially during mid-lactation) and calf growth and, to a lesser degree, by increasing (P>.05) fatness. These differential responses resulted in large differences in heterosis for the two pasture types. Calculated heterosis values were relatively large for average female weight and fatness of females grazing fescue-legume, and for weaning weight for those grazing fescue.